The job option enable the usage of pipes to communicate with sub-makes.
On MINIX, it seems that there is possibility of receiving an EAGAIN on
such reads, even when it had previously been tested for POLLIN using
poll().
This patch is a workaround, by wrapping the read operation within a
do {} while(errno == EAGAIN && ...) loop.
Change-Id: Ia184c4d600efe7218d197820df87761604120862
7d98eee859